Apparatus for straightening hot-rolled tubes



3,534,575 APPARATUS FOR STRAIGHTENING HOT-ROLLED TUBES Filed July 7; 1967 H. DE CORTA Oct. 20, 1970 e s-sheet 1 INVENTOR HUBERT J a C RTA BY fl LW/ ATTORNEY APPARATUS FOR STRAIGHTENING HOT-ROLLED TUBES Filed July 7, 1967 H. BE CORTA Oct. 20, 1970 2 Sh-eetsSheet 3 INVENTOR de CORT Y ATTORNE Y3 United States Patent 93 Int. Cl. B21f 27/ 06:39/ 00, 43/04, 45/02 US. Cl. 72-201 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to improvements in apparatus for straightening hot rolled tubes. The apparatus comprises a number of parallel rolls set closely together with their axes horizontal and the rolls are driven to rotate in the same direction. The hot rolled tubes are fed onto the rolls in a plastic or semi-plastic condition with their direction of length substantially parallel to the rolls and move along the rolls, being straightened and cooled in the process. In accordance with the invention, at least some of the rolls are profiled to allow the passage of cooling air between adjacent rolls.

BACKGROUND OF THE INVENTION Hot rolled tubes generally require to be straightened when they have been formed.

A straightening machine of the conventional type generally comprises a set of parallel rolls arranged as closely together as possible with their axes horizontal and driven in such a way that they all rotate in the same direction. These rolls, which usually have a distinctly larger diameter than that of the tubes it is required to straighten, are internally cooled by water circulation. The tubes to be straightened, the temperature of which may be 850 C. to 900 C., for example, are in a plastic or semi-plastic state when discharged on to the straightening machine in a direction substantially parallel to the rolls. They are caused by the first two rolls to rotate about their own axes and then progress from roll to roll, in the course of which they are straightened as they cool. However, the cooling of the tubes by contact with the cooled rolls is limited, since the zone of contact with the rolls at any given moment is restricted to two lines of contact along their length. Moreover, the water used for cooling the rolls attains a fairly high steady temperature. Upon discharge from the straightening machine, therefore, it is advisable to continue cooling the tubes by moving them across grids, which, apart from their complication, have the disadvantage of taking up considerable space. The cooling is finally completed by immersing the tubes in tanks filled with water; but when the tubes are still relatively hot, this operation produces large clouds of steam, which is an additional drawback.

SUMMARY The disadvantages referred to above are, at least to a material extent, overcome by the apparatus of the instant invention which provides that some at least of the rolls, and preferably the final rolls, are profiled to permit the passage of cooling air upwards between adjacent rolls thereby promoting cooling of the tubes and of the rolls. This profile may be provided by indentations on the rolls so that the tubes are supported on set-out portions of the profile during straightening whilst at the same time cooling air can be blown upwards between the rolls through the passages provided by the indentations. The set-out portions of the profiled rolls should preferably be staggered from roll to roll so that the profiles of adjacent rolls can mate. The profiles can be provided by axially spaced annular ribs on the rolls or by helical ribs. The advantage of the latter is that the points of contact of the hot tubes with the helical ribs vary constantly as the tubes and the rolls rotate and marking of the tubes is avoided.

The blowing of cooling air which is thus made possible between adjacent rolls enables the tubes to be elfectively cooled. Therefore, the grids of the known apparatus can be eliminated or reduced or the total number of rolls in the straightening machine can be reduced, or, again, the immersion of the tubes in water can be dispensed with, failing which, at all events, the formation of great clouds of steam can be avoided. By combining the circulation of water for cooling the rolls and the circulation of air for cooling the tubes, it is possible to cool the tubes so that their temperature when they leave the straightening machine is below C., for example.

When the tubes to be straightened are of small diameter, it is advantageous to apply the arrangement here proposed to all the rolls in the machine, because, by virtue of the interlocking profiles, one can practically eliminate any risk of small tubes being wedged between the rolls, as has happened with the plain rolls in use hitherto.

Some presently preferred embodiments of the invention will now be described by way of example, reference being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic end elevation of a straightening machine embodying the present invention;

FIG. 2 is a diagrammatic plan showing part of the straightening machine seen in FIG. 1;

FIG. 3 is an enlarged cross-section of cooling rolls conforming to the invention; and

FIGS. 4 and 5 are diagrammatic representations of alternative shapes for these rolls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The roll-type straightening machine shown in FIGS. 1 and 2 incorporates a number of hollow parallel rolls set as close together as possible with their axes in one horizontal plane. Each roll is supported in the conventional manner by suitable mid-supports, such as 1, and each of its ends rotates in bearings, one of which forms part of a driving assembly 2, enclosing gears by which uniform rotary motion in one and the same direction can be imparted to all the rolls, the power being provided by a motor 3. The hollow rolls are cooled internally by water circulation from a header, 4. The running of the machine can be operated and supervised from the desk 5.

In existing straightening machines of this type, all the rolls are plain and as close together as possible, leaving between them only the amount of play necessary for satisfactory operation, to enable small-diameter tubes to be straightened without the risk of such a tube becoming wedged between two adjacent rolls. Such closeness of the rolls, however, prevents cooling air from being blown efiectively between them, so that the ordinary cooling of the tube is poor, being derived mainly from radiation to the interior-cooled rolls and only secondarily from the conduction of these rolls, with which the tubes are in contact, at most, at two positions of the roll generator line.

According to the invention, at least the last two rolls of the straightening machine are given an indented profile, so that the machine comprises one set of rolls, 6a, 6b 6n, the prime function of which is to straighten the tubes, incidentally cooling them, followed by a second set of rolls, 7a, 7b 7m, the prime function of which is to afford intensive cooling of the tubes while completing the straightening process.

The rolls 6 are plain cylinders, arranged as in conventional straightening machines. The rolls 7 have an indented profile such that the set-out portions support the tubes and cause them to rotate about their own axes while straightening them, while the set-in portions permit the passage of cooling air circulated by means of an air duct 8, situated below the level of the rolls, from a suitable blower 9.

The set-out portions should preferably be staggered from roll to roll, to enable the profiles of adjacent rolls to mate or interlock. These setout portions may be formed from separate rings or annular ribs fixed or disposed at regular intervals along a core consisting of a plain hollow cylinder, 10.

In the example shown in FIG. 2, the portions in relief are formed from axially short rings or ribs, 11, fixed to the core 10 and spaced longitudinally apart effectively leaving grooves between the ribs. The rings on one roll are offset longitudinally with respect to those on the adjacent roll to enable the rolls that support the tubes for straightening by the rings to be brought as closely together as possible, while still leaving sufficient space between the cores 10 to enable the cooling air to pass through.

In the variant shown in FIG. 4, the indented profile of the roll is obtained by the provision of axially short rings or ribs 12, spaced longitudinally but closer than the rings or ribs 11 of the previous example. The profiles of adjacent rolls interlock and the advantage of this arrangement is that it provides better support for the tubes that are being straightened, without the rolls having to be fitted so closely together. 7

In the alternative form shown in FIG. 5, the indented profile is obtained with the aid of rings or ribs 13, disposed substantially in the same way as in FIG. 4, but axially longer than those of the previous example, so that the number of rings can be reduced while ensuring proper support for the tubes and still leaving an adequate gap for the passage of cooling air.

Various other shapes are naturally possible. For instance, the set-out portions may take the form of helical ribs, disposed in such a way that the profiles of adjacent rolls interlock as they rotate. In that case, the helical pitch should preferably be the same on each roll.

Whichever design be chosen, the cross-sectional arrangement arrived at will be that shown in FIG. 3, which shows one plain roll, 6n, followed by rolls with indented profiles, 7a, 71) etc. The tubes T progress over the rolls of the straightening machine in the direction of the arrow F, rotating about their own axes by reason of the rotation of the various rolls. The tubes T, already straightened and partially cooled by the set of rolls 6, come to rest, parallel to the rolls, initially between the plain roll 6n and the set-out portion11, for exampleof the roll 7a and then between the set-out portions of the rolls 7a and 7b. The various rolls are cooled internally bywater circulation, but, in addition, air is blown upwards through the spaces available between the cores 10 of the interlocked rolls. This air eflectively cools the tubes T as they rotate about their own axes.

Again, instead of arranging for all the rolls to turn at the same speed, the peripheral speed of the rolls can be increased in succession from start to finish throughout the machine, so that, because of the differences in relative tangential speed between successive rolls, the tubes tend to move out of the space situated between these. The variation in tangential speed can be obtained by varying the angular velocity of rolls of equal diameter, by varying the 4 a diameter of rolls having equal angular velocity or by a combination of these two possibilities.

It will, of course, be appreciated that forming the rolls with axially spaced rings or annular ribs is equivalent to forming the rolls with axially spaced annular grooves or channels. Similarly, the provision of a helical rib is equivalent to the provision of a helical groove.

It will also be appreciated that the grooves need not necessarily extend completely around a roll. Thus the grooves could extend only partly around a roll, the grooves being staggered circumferentially and adjacent grooves overlapping circumferentially so that in all angular positions of the roll there is a plurality of grooves extending through the bite between adjacent rolls to allow the passage of cooling air therethrough to the tubes supported above.

I claim:

1. Apparatus for straightening and cooling hot-rolled tubes comprising a series of hollow rolls with their axes substantially horizontal, means for circulating cooling water through said hollow rolls, means for feeding hotrolled tubes in plastic to semi-plastic condition to the first roll of said series of hollow rolls with the axes of said hot-rolled tubes parallel to said hollow rolls, said series of hollow rolls being set closely together side by side at a distance of less than the diameter of said hot-rolled tubes, means for rotating said rolls in the same direction whereby said hot-rolled tubes fed to the first roll of said series of hollow rolls are advanced over said series of hollow rolls, the first rolls of said series of hollow rolls considered in the direction of advance of said hot-rolled tubes being rolls having a plane surface while the remaining rolls of said series of hollow rolls being provided with grooves arranged and disposed so that at all angular positions of adjacent rolls a plurality of grooves extend through the bite of adjacent rolls, and means for blowing cooling air through said grooves extending through the bite of adjacent rolls, whereby said hot-rolled tubes in plastic to semi-plastic condition are partly cooled and straightened on passage over said first rolls having a plane surface and are further cooled on passage over said remaining rolls provided with grooves.

2. The apparatus of claim 1 wherein said grooves on said remaining rolls of said series of hollow rolls are arranged as a helix with ribs separating the grooves, said ribs of one roll extending into grooves of the adjacent rolls for the purpose of providing a continuous support for said hot-rolled tubes.

References Cited UNITED STATES PATENTS 265,265 10/1882 Kellogg 7269 1,675,949 7/1928 McKee 3462 1,750,534 3/1930 McArthur 72202 1,758,699 5/1930 Hazeltine 7298 2,199,130 4/1940 Hazeltine 7298 2,542,940 2/1951 Pioch et a1. 148-156 2,895,190 7/1959 Bungeroth et al. 164-282 3,452,785 7/1969 McLean et al. -Z 3,390,871 7/1968 McLean et al. 140-2 FOREIGN PATENTS 87,351 8/ 1921 Austria. 1,026,941 4/1966 Great Britain.

CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant Examiner US. Cl. X.R. 

